Telephone system



June 19, 1934. s. T. BAKER V 1,963,929

TELEPHONE SYSTEM Filed July 18, 1932 12 Sheets-Sheet 1 INVENTOR GEOR6E THOMAS BIIKEI? ATTX June 19, 1934. G. T. BAKER TELEPHONE SYSTEM 12 Sheets-Shee t 2 Filed July 18, 1952 MOL 7 mm I INVENTOR GEORGE THOMAS BAKER ATT).

June 19, 1934. G, T. BAKER 1,963,929

TELEPHONE SYSTEM Filed July 18 1932 12 Sheets-Sheet 3 E H a ii fi 9 9 F v5 IN VENTOR GEORGE THOMAS BAKER ATTY.

June 19, 1934. G. T. BAKER TELEPHONE SYSTEM Filed July 18 1932 12 Sheets-Sheet 4 ilos mm M 49 Pic- INVENTOR GEORGE THOMAS BAKER ATT).

June 19, 1934- G. T. BAKER 3 5 TELEPHONE SYSTEM Filed July 18 1932 12 Sheets-Sheet 5 /N VENTOR GEORGE THOMAS BAKER ATTY.

June 19, 1934. G. T. BAKER 1,963,929

TELEPHONE SYST M 7 Filed July 18 1932 12 Sheets-Sheet 6 INVEN'TOR' GEORGE THOMAS BAKE/3 ATTK June 19, 1934. BAKER TELEPHONE SYSTEM Filed July 18 1932 12 Sheets-Sheet 7 /NVENTOR GEORGE THOMAS BAKER ATTX June 19, 1934. G. T. BAKER 1,963,929

7 TELEPHONE SYSTEM Filed July 18, 1932 i2 sheets-sheet 8 INVENTOR GEO/36E THOMAS BAKER ATT).

Filed July 18, 1932 I 12 Sheets-Sheet 10 INVENTOR GEORGE moms BAKER ATTY.

, June 19, 9 G. T. BAKER 1,963,929

TELEPHONE SYSTEM Filed Ju1y l8, 19:52 12 Sheets-She et 11 I ar QE INVENTOR GEORGE THOMAS BAKER ATTY.

June 19, 1934; G. 1'. BAKER TELEPHONE SYSTEM Filed July 18, 1932 12 Sheets-Sheet. 12

INVENTDR GEORGE THOMA5 BAKER ATTK Patented June 19, 1934 UNITED STATES 4 PATENT OFFICE TELEPHONE SYSTEM ware Application July 18, 1932, Serial No. 623,071

In Great. Britain July 29, 1931 14 Claims.

The present invention relates to telephone systems and is more particularly concerned with systems employing register controllers of the code translating type in which series of impulses transmitted by the calling subscriber and representing the exchange code are received by the register controller and translated into series of impulses having no relation to the impulses received from the calling subscriber.

The principal object of the invention is to provide a register controller of the above type particularly suitable for use in a rural exchange system of small capacity. In a system of this type it is probable that a certain number of the subscribers associated with the rural exchange will be party line subscribers. Since such subscribers are not provided with automatic meters to assess the charge for a call it will be appreciated that ona cal1 to a distant exchange an operator will have tobe brought in to complete the connection and assess the call.

According therefore to one feature of the invention in such a system. when a connection originates from certain types of calling lines the register controller employed in setting up the connection is arranged to transmit a series of routing digits characteristic of the calling line. It will be appreciated that the invention is not limited to party line subscribers but is capable of application to other types of calling lines for instance to subscribers setting up a connection from a public call oflice. Further in view of the somewhat difierent nature of the work involved it is convenient that calls from party lines and coin box subscribers should be routed to diiferent operators for the assessment of the charge.

In the system described in the detailed description it is assumed that the rural exchange is situated near to a main exchange. Further all outgoing calls from the rural exchange are extended through the main exchange and consequently if the provision of an additional rank of switches at the main exchange is to be avoided, it is necessary that the exchange codes of both the rural exchange and main exchange should be the same. Special discriminating means must therefore be provided in the register controllers at the rural exchange since the dialling of the exchange code is not sufiicient to determine the destination of the calling and according to a ment both local subscribers to the main exchange and subscribers on the rural exchange will be accessible over different levels of the same rank of switches.

A still further feature of the invention relates to the provision of a selector switch for use in conjunction with a register controller at the rural exchange and which may function'either as a final selector switch if the call is a local one or as a firstcode selector switch if the call is for another exchange. In order to maintain a uniform numbering, scheme provision is made ac-? cording to a further feature of the invention for absorbing certain digits when a local call isset up directly by the calling subscriber, in which case W the register controller-is released.

A further feature relatesto an arrangement for enabling a party line-subscriber to call another party line subscriber on the same line by diallinghis ordinary directory number, the trunk relay group associated with the code or local selector alone being connected up.

Further features of the invention relate to arrangements for catering for party lines having a large number of subscribers on the same line 39 say up to ten and for enabling party line subscribers to become individual line subscribers without changing their number. I

The invention will be better understood from the following description of one method of carrying it into effect, taken in conjunctionwith the accompanying drawings comprising Figs, 1 to 12 which should be arranged as shown in the key sheet contained in Fig. 9 to form a complete circuit. Figs. 1, 2 and 3 show a subscribers line 85 circuit together with a line finder associated with the line circuit over a finder distributor FDS shown in Fig. 3; Figs. 4 and 5 show a selector switch directly associated with the finder switch and adapted to operate as a final selector or a first code selector depending upon whether the call is local or for a distant exchange. When operating as a. first code selector the switch provides access to 10 outgoing junctions, while' when operating as a final selector the switch has access to 100 subscribers lines. Meter discrimination up to 6 zones is provided on calls originated by regular subscribers. Figs. 6, 7, 8 and 9 s'how a register controller which in addition to performing the well-known functions provides three different translations for the same digits dialled according to the type of calling line, and further on local calls provides discrimination on the first numerical digit. The register controller is associated with the selector switch over a selector finder switch SFS which in turn co-operates with a translating distributor switch shown in Fig. 10 to associate the selector switch with an idle register controller. Figs. 11 and 12 show the ringing, tone and pulse supply circuit.

Returning now to the assembled circuit and assuming that the subscriber associated with the line circuit shown in Fig. 1 originates a call a circuit is completed by way of his instrument over conductors 10 and 11 to energize relay LK over its resting armatures Zk3 and 1704. Relay LK makes a first stage operation only in this circuit to close the light armatures llcl and llc2, and the high non-inductive resistance which is included in its operating circuit and shown to the left-hand side of the coil ensures that the resistance of the subscribers circuit has no appreciable effect on the operation. Relay LK at armature Zkl extends battery from the coil to mark the calling subscribers position in the rotary bank multiple, and at armature lk2 extends battery over the level start common 12 to mark the calling level in the vertical bank multiple and at the same time operating the common start relay S, Fig. 3, by way of the resistance 13. Relay S at armature s1 completes a circuit for operating relay V over both its windings in series, and at armatures s2 and s3 completes the circuit for 4 the delayed alarm relay set TA and TB, the

function of which will be described later. It should be explainedat this point that the distributor switch FDS is preselecting so that it always positions its wipers in engagement with a free finder such as that shown in Fig. 2 and if at the instant the call is made the wipers are resting'on contacts extending to a finder which is already in use, the following circuit is completed for advancing the wipers into engagement with the next free finder: earth on wiper 5a and bank contact, derived from the operated armature 171.3 in the case of a finder which isalready switched or alternatively, by way of the offnormal springs 1N2 and resistance 14 in the case of a finder which is performing its setting move-- ment, upper low resistance winding of relay V, armature v2, interrupter springs fdm, right-hand winding of relay G to battery. Owing to its high resistance relay G only is operated in this circuit and at armature g1 energizes the driving magnet FDM to prepare for the advancement of the wipers on to the next set of bank contacts. At the conclusion of the magnet stroke the interrupter springs fdm open the circuit to relay, G which releases and in turn de-energizes the driv- =ing magnet FDM so that the wipers move into the next position. By this means an alternate action takes place between relay G and the magnet until the wipers are moved into engagement with the next available finder, in which position wiper 5a encounters an idle'marking battery exe tended from the resistance 15 and the resting contact of the off-normal springs 1N2, whereupon the driving circuit is terminated since there is now no circuit for operating relay G. Consequently uponthe operation of the start relay S, relay V then operates over both its windings in series, and the low resistance of the marking battery is sufficient to short-circuit relay G against'operation at this time. Relay V provides an alternative locking circuit for itself at armature 121 to battery by way of resistance 16 which is of approximately the same resistance as the idle marking battery 15, and at armature 02 opens the circuitto relay G and short-circuits its lower winding so that the relay then holds over the low resistance upper winding thereby effectively guarding the finder taken into use from selection by another distributor. Relay V moreover at armature 127. extends battery by way of resistance 17, wiper 6a and bank contact of the switch FDS, conductor 18, resting contacts of armature 1716 in the finder selected, lower speaking conductor 19 to operate relay L, Fig. 4, of the associated selector over its lower winding. Relay L at armature ll operates relay B and at the same time removes earth from the release trunk conductor 20 extending to the release magnet circuit of the finder. Relay B, Fig. 4, of the selector in turn operates relay BB shown in Fig. 5 which at armature bbl, Fig. 4, connects earth to the release trunk conductor 21 to guard the circuit and prepare for the subsequent holding of the .preceding switches.

Furthermore, relay V in the distributor circuit at armature v9 completes a circuit for energizing the vertical magnet of the finder over wiper 8a and bank contactof the switch FDS andconductor 22, and at the conclusion of the magnet stroke when the wipers are raised to their first position, the springs um will close thereby applying earth to conductor 23 which completes a circuit over bank contact and wiper 4a of the switch FDS to energize relay G over its right-hand winding. vIn this manner relay G is now caused to interact with the vertical magnet of the finder so that the wipers are raised to the marked level. Towards the end of the first vertical step, the off-- normal springs are operated thereby at springs 1N1 preparing a circuit to the release magnet ZM, at springs 1N2 connects up earthby way of the resistance 14 to the'bank contact of the switch FDS, and at springs 1N3 removes battery from the lower winding of relay 1H. The connection of earth by way of the off-normal springs 1N2 to the bank contact of the'finder distributor is without efiect at this time since the circuit is' already guarded from earth extended via the winding of relay V, but the feature is necessary to guard the finder against selection when the wipers are moved from their normal position during exchange tests.

When the wipers of the finder are raised to the marked level the vertical wiper VW encounters the marking battery extended from the level start conductor 12 in the line circuit, and consequently when relay G operates due to the closing of the springs cm at the end of the vertical movement, a locking circuit is then completed from battery on the vertical wiper VW over conductor 24, bank contact and wiper 2a oi. the switch FDS,

r4 supplements the operation of the start relay S which releases owing to the application of guarding potential by way of the low resistance winding of relay R to the vertical bank, at armature r5 the circuitis opened to the driving magnet of the distributor and at armature r6 the driving circuit to the finder is transferred by way of wiper 7a and-bank contact over conductor 25 to the rotary magnet RM. Upon the release of relay G the rotary magnet is energized to advance the wipers of the. finder into engagement with the level selected, and at the conclusion of the magnet stroke, springs rm are closed thereby completing a circuit for re-operating relay G which may be traced from: positive at the armature 124, Fig. 3, wiper 3a and bank contact of the switch FDS, conductor 26, lower winding of relay 1H, armature lhl, springs rm, conductor 23, bank contact and wiper 4a of the switch FDS, armature v3, winding of relay G to battery. Alternatively in case the first set of contacts in the bank are not those marked, wiper P will encounter'earth or a disconnection depending upon the condition of the line circuit connected therewith. In the case when earth is present on the contact signifying that this line circuit is in use, a circuit will be completed by way of the upper winding of relay 1H which augments that already traced via the wiper of the distributor. In this manner relay G interacts with the rotary-magnet RM to bring about the advancement. of the wipers into engagement with the calling line which is marked by the presence of battery potential through the winding of the cut-off relay LK. Towards the end of the first rotary step the rotary off-normal springs operate thereby opening a circuit to the switchingrelay 1H which is effective for guarding purposes in case the associated selector is taken into use for test purposes.

Under these circumstances the engagement of the selector other than over the normal route will be indicated by the application of earth to the release trunk conductor 21 and finds a circuit by way of the springs lNRl, lower winding of relay IE to battery by wayof the off-normal springs 1N3. Relay IE is operated in this circuit and at armature 1h3 connects earth to the corresponding contact in the bank of the distributor switch FDS to guard the finder against selection.

Returning now to the normal progress of the call, when the wipers are moved into engagement with the calling line, relay G is short-circuited against further operation by the presence of marking battery encountered by wiper P, which also serves to operate the switching relay 1H over both its windings in series. Relay 1H at armature lhl completes a locking circuit for itself over its upper low resistance winding to earth on the release trunk conductor 21 from the associated selector, at armature 1h3 connects direct earth over conductor 2'7.to busy the circuit in the distributor bank, and at armatures 1h6 and 1h7 extends the calling subscribers instrument circuit to the associated-selector. Relay LK of the calling circuit is fully operated in series with the switching relay 1H in the finder to clear the line of its normal battery and earth connections, and at armature Zk5 removes battery from the level start common 12. Relay V is short-circuited and released by the connection of direct earth at armature 1h3 and when the armature '02 becomes normal, relay G is re-energized in series with the upper low resistance winding to complete a circuit for the driving magnet FDM in order that the wipers of the distributor shall be moved out of engagement with the busy finder.

In case the next finder is also in use the distributor FDS will continue its hunting operation in the manner already described to preselect the first available finder preparatory to the reception of a further call.

It should be explained that two distributors such as FDS and associated relays are provided and although the second is not shown in detail the associated start relay 1S and change-over contacts are indicated to the'left-hand side of Fig. 3. Both distributor switches have access to the same group of line finders, the arrangements being such that if one switch fails the other switch takes over the duty and the necessary changeover is made from a delayed timing set in a manner which will now be described.

Assuming that the finder taken into use fails to switch through within a reasonable period of time the continued operation of relay S or R maintains earth to the start terminal TPS extending to Fig. 11 for the purpose of setting in operation the tone and time pulse equipment whose detailed operationsvwill be fully described later. It will be suificient at this period to say that after a short interval earth is connected to the terminal FDS from this equipment which serves to operate relay TA over its right-hand winding so that'the relay then looks over its lefthand winding to earth on armature $4, or alternatively earth by way of the restingvarmature lh4 of the finder taken into use. over at armature m2 connects one winding of relay TB to the terminal FDZ and after a time Relay TA moreinterval ofconveniently 9 seconds after the application of earth to the terminal'FDS, an earth pulse is then connected to the other terminal FDZ whichserves to operate relay TB which looks over its other winding in circuit with a resting armature of relay TB in the auxiliary distributor circuit to earth over conductor 57 supplied by way of an alarm circuit not shown. Relay TB moreover at armature tb2 releases relay TA and at armature tb3 transfers the start circuit to relay 1S so that all further calls will be completed over the auxiliary distributor.

Incoming junctions from other exchanges'are terminated after the fashion of an ordinary subscribers line on a combined line and cut-off relay such as LK, and in order that incoming calls shall not be delayed owing to the distributor being busied in'the process of connecting up a local call, the start circuit from LK relays of incoming junctions is diverted to bring about the opera tion of the start relay 1S, so that all junction calls are completed by way of the auxiliary distributor which is not normally used for local calls. Such an arrangement has the effect of speeding up the incoming traffic and is particularly desirable in cases where the finder has to locate the calling line between successive digits.

Since the finders are required to serve linesonly there is no limitation as to the number of wipers available and hence-forth wire metering may be adopted with advanta'ge owing to the fact that metal rectifiers will not be required in the meter circuit and the necessity for a booster battery installation also disappears. Meters are not provided or'rparty lines and the'meter contacts on the party line level are wired back to the vertical bank of the selector for a purpose which will be described later. 7

Referring now to Figs. 4 and 5 this circuit is arranged to serve four different types of traffic which may be classified as'follows:--

(a) Calls incoming from a distant exchange.

(1)) Local subscribers desiring local connection.

(0) Local subscribers requiring a distant exchange.

(d) Revertive calls.

The first two types may again be'sub-divided according to whether the called party is situated on an individual or a party line.

Considering first a call incoming from a distant exchange, it should be explained that the bothway junction lines terminate in the local exchange on level 1 of the line finders, and consequently when the finder selected switches on this level, earth is extended by way of the operated armature 1h4, Fig. 2, vertical wiper VW and first bank contact, conductor 28, to operate relay .110, Fig. 4, of the associated selector. It should also be noted that'as this exchange is not arranged for tandem traffic, all calls incoming from a distant exchange are intended for local subscribers, and therefore, as a resultof the discriminating signal extended over conductor 28, relay L0 in operating converts the switch into a final selector, in order that the wipers may be set both in a vertical and. rotary direction under the control of impulses.

The incoming junction extended by way of the wipers and the switching relay armatures of the finder taken into use, completes a circuit for the line relay L, Fig. 4, which in turn at armature l1 closes a circuit for relay B. Relay B operates and at armature b1 closes a circuit for relay BB, Fig; 5. Relay BB at armature bbl, Fig. 4, connects earth to the release trunk conductor 21 to guard the switch and hold operated the switching relay 1H of the finder and relay LK of the line circuit terminating the junction, and moreover .at armature bb3, Fig. 4, operates relay C on its upper Winding. Owing to the operation of relay LO immediately the switch is seized, circuits are opened at armatures Z01 and Z08 extending to the register controller group, since the switch is to function'as the final selector and there is no question of storing or translation. As the call in question is originated from the first numerical selector level of the main exchange there remains with the particular numbering scheme chosen, three digits to be used in the local oflice, and as the switch therein will be set by the last two digits only, it is necessary that the first of the three shall be absorbed. I

For all incoming calls the first digit received at the local exchange is 7, and in response thereto relay L is impulsed and at each de-energization completes the following circuit for energizing the vertical magnet 2VM in order that the wipers may be stepped to the 7th level: earth at the resting springs 'of armature 11, Fig. 4, armatures ba2, 12b2, 2FL4 and cl, low resistance lower winding of relay C, armatureel, winding of vertical bank 2VM to battery. Towards the end of the first vertical step the off-normal springs are operated thereby at springs 2N1 opening the initial energizing circuit to relay C, at springs 2N2, Fig. 5, a point is closed in the circuit of the release magnet 2ZM and at springs 2N3, Fig. 5, a point is prepared in a tone circuit which becomes effective in case the desired subscriber is unavailable. Although the original energizing circuit to relay C is now opened, the relayremains held during the impulsing period over its lower winding by reason of the copper slug surrounding its core. Relay B is similarly equipped with a copper slug in order that it shall be held operated continuously during the impulsing period. At the conclusion of impulsing when the wipers are set opposite the'lth level, relay L is then held operated for an extended period, so that relay C releases after a'short int'efla'l and the following circuit is completed for energizing the release magnet in order that the shaft and wipers shall be restored to the normal position: earth at. armature 2h2, Fig. 5, armaturercl', springs 2N2, armatures b2 and Z03,

rotary off-normal springsr'2NRl, armatures c2.

and da2,- vertical bank contacts VB which are relay DA is no longer short-circuited, it operates in series with the release magnet 2ZM and locks for the remainder of the connection over its other winding toearth at armature bb4, Fig. 4.

Relay DA at armature da2 prepares a circuit for operating relay E at the conclusion of the next impulsing period, and' at armatures da5,.da6 and da 'l establishes connection with the upper set of wipers negative 1, positive 1 and P1 which have-access to the local hundred group of lines.

The second digit received again steps the shaft and wipers vertically, and at the conclusion of the impulse train when relay 0 releases, relay E then operates owing to the changeover at armature' (M2, and at armature e1, Fig. 4, connects up the rotary magnet 2RM, at armature e4 connects earth to conductor 29 to operate relay C, Fig. 4, over its upper winding, and atarmature e5 prepares a locking circuit for itself which becomes effective when relay C again operates.

Upon the reception of the third digit the rotary magnet 2RM is responsive to advance the wipers into engagement with the desired line, and towards the end of the first rotary step the rotary off-normal springs are operated thereby at springs 2NR1, Fig. 5, preparing a circuit. to relay M and at springs 2NR2 a circuit is prepared to relay CO, Fig. 4, which is however not effective on this type of call.

At the conclusion of the third series of impulses, relay L is again held operated and upon the release of relay C and duringthe slow release period of relay E, a circuit iscompleted for operating the switching relay 2H on its right-hand winding in series with the LK relay of the called subscriber's line circuit; Relay 2H then locks on its left-hand winding by way of the light armature 2h1 in series with the upper winding of relay A which is not operated in this circuit owing to the high resistance ofrelay 2H, at armature 2722 apoint is opened in the circuit to the release magnet 2ZM, at armature 2h3, Fig. 4, relay CO is operated, at armature 217.4 the impulsing circuit is opened to the driving magnets of this switch and at armatures 2h5, 211.6 and 2h? the connection is extended to the called subscribers line circuit in readiness for the transmission of ringing current.

Relay CO it should be explained locks for the remainder of the call by way of its armature col, at armature 003, Fig. 5, connects earth by way of the resting armature (Z26 to the common start. lead 'TPS extending to the ringing tone and pulse supply equipment shown in Figs. 11

and 12, and moreover at armatures 005 and 006- completes still further points in the ringing cirto the upper-speaking conductor and the called subscribers instrument from whence a return circuit is completed over the lower speaking com a ductor to ring-return battery by way of the resistance connected to the resting armature f5. In order to inform the calling subscriber that the call is proceeding satisfactorily a leak on the main ringing circuit is provided by way of the operated armature e04, oil-normal springs 2N3 and condenser QD to the upper speaking conductor'on the calling side of the circuit, and has the efiect of producing a tone in the calling subscribers receiver characteristic of the ringing periods. If, however, the called subscribers line terminated on contacts situated on one of the upper three levels, ringing is then picked up from the bankcontacts by way of wiper positive 2 and extended over the normal post springs NP which are operated on these levels to the winding of the ring-trip relay F. The type of ringing extended now depends on whether the called sub-' scriber has an individual line or whether he is situated on a party line. In the former case wiper positive 2 will rest on a contact to which is connected standard ringing such as is connected up by way of the resting normal post springs, while in the latter case wiper positive 2 will pick up the required code ringing from one of the terminals CDRl to CDRlO shown in Fig. 12.

All party line subscribers are allocated a separate directory number and those which represent the same party line are multipled together on the bank. Thus assuming that on level 9 subscribers 9l--9394-95 and 97 are situated on the same party line while the remainder of the subscribers on this level have individual lines, then the negative, positive and P1 contacts of the partyline numbers will be connected together, whilethe corresponding contacts in the bank associated with wiper positive 2, will be connected to difierent code ringing terminals such as for example CDRl to CDR5 shown in Fig. 12. Similarly the contacts in the bank associated with wiper positive 2 corresponding to the individual subscribers numbers 92-969899 and'90 will be connected together and extended to the standard ringing terminal chosen, in this case assumed to be CDRl.

It will now be convenient to describe the manner-in. which the various tones, time and meter pulses and code ringing signals are produced, for which purpose reference will now be had to Figs. 11 and 12. The equipment shown in these figures is common to the exchange and when any portion of the exchange equipment requires either tones, pulse supply or code ringing, earth is connected to the common lead TPS shown extending from Fig. 11 to bring about the operation of the start relay MS. Relay MS at armature msl completesvibratorcoil so that the pendulum member swings away from the pole pieces to close the left-hand contacts oil). In this manner the pendulum member is caused to oscillate and the movement i maintained indefinitely so long as the circuit is closed by the interacting effect of relay P.

Connected in circuit with the vibrator contacts 'nected to battery at its mid-point by way of the impedance I. Each half of the transformer winding is energized alternately and in opposite polarity from the oscillating vibrator contacts and by induction into the secondary winding the two half waves are combined to form alternating ringing current which is smoothed to some extent by the presence of the condensers QA and QB connected to earth by way of resistance. An alternating current relay AC is connected to the output terminal of the secondary winding of the transformer and as soon as the alternating current is generated this relay operates, and at armature acl transfers the energizing circuit for the vibrator'coil to earth by way of a comparatively highresistance, which has the efiect of reducing the current to a value sufiicient to maintain smooth vibratory motion of. the pendulum, without undue hammering on the pole pieces of the coil. The alternating current relay AC is of the usual type used in telephone systems connected in bridge with a metal rectifier MR0, and its function is now generally well recognized. The current interruptions in the primary winding of the transformer XFR are also used to provide dial tone, which is extended by way of the armature p2 and condenser QG to the feed terminal DT. Busy tone is generated by relay 1BR which is connected up at armature ms2 and arranged to energize in a self-interrupted circuit that is to say, on the opening of the armature 11211 a high resistance is inserted in series with the energizing coil which reduces the current below the operating value of the relay so that it releases, and again becomes energized in series with its armature lbrl. In this manner a buzzing operation' of approximately 400 cycles per second is produced and by induction a tone is generated in the low resistance upper winding corresponding to number unobtainable tone and extended by way the drawings INTI to INT4, employed for interrupting the tone circuits and for producing a time pulse to operate delay sets in the exchange equipment. Relay IR is arranged to interact with the driving magnet INM so that the movement iscontinuous so long as the start relay is operated, and the interacting operation is slowed down to some extent by thepresence of the slug on relay 1R which reduces the speed of operation to about .18 seconds for each cycle, and as 50 steps are required to turn the cams through one revolution the time occupied is therefore approximately 9 seconds. Referring to the timing cams INTI and INTZ, it will be appreciated that earth is momentarily connected to the common conductor FDS and approximately 9 seconds later earth is momentarily connected to the common conductor FDZ. Springs controlled by the cam me which produce an interruption of .75 secondson and .75 seconds 01f are introduced into a parallel feed 1 5 from the NU tone s pply which extendsbyway of the condenser QF to the terminal BT to provide a busy tone feed.

The springs associated with cam INT4 which produce an interruption of .2 seconds on and .2 50

seconds 01f are introduced into the circuit of the driving magnet-CRM of the code ringing switch CRS, Fig. 12. Continuous ringing is extended from the secondary winding of the transformer over conductor 30 to the wipers 1b to 5b of the code ringing switch CRS, the bank contacts of which are connected together to produce the required ringing codes such as indicated diagrammatically in the drawings by long and shortdashes opposite the feed terminals CDRl to CDRlO. As the driving magnet of this switch is being energized from an earth pulse of .2 seconds on and .2

seconds ofi it willbe appreciated that the wipers rest on the contacts for .4 of a second, and from a consideration of the wiring, it will be seen that the short ringing'periods have a duration of .4 of a second, while the long periods will have a duration of 1.2 seconds.

When the wipers of the code ringing switch come to the end of the code ringing cycle, wiper I vided for the purpose of supplying zone metering pulses to the exchange equipment, and is controlled from the armature 2'11, Fig. 11. Relay IR as already explained is interacting with the driving magnet of the interrupter switch at a cycle speed of approximately 1.8 of a second, and it therefore follows that the wipers of the switch MPS will rest on each contact for an equivalent period. In addition to the actual zone meter pulses which efiect the operation of the calling subscribers meter this switch also controls the application of timing pulses to the meter delay set, and for this purpose when wiper 1c of the switch encounters the second bank contact earth is connected to the common pulse lead MP8, and after a short delay period sufficient to prove the positive operation of the metering relay in the exchange equipment, earth is then extended over the common conductor MPZ, to cause the meter ing operation to commence. Moreover, as the MIPZ lead is commoned over a number of contacts in the bank it will be seen that this pulse persists throughout the whole metering period. At the completion of the metering pulse cycle, wiper 60 leaves the first common set of contacts and engages the second common set from which a selfinterrupted circuit is completed to the driving magnet MPM to restore the wipers to their starting position, from which they may then start out on another metering cycle providing that the start relay MS is maintained operated from other Relay F at armatures f4 and f5 completes thetransmission circuit between the calling and called subscribers and relay I which functions as a battery feed to the called subscriber operates over the line in series with his instrument circuit and at armatures i1 and i2 reverses the battery over store the shaft and wipers to normal.

.ing by way of the linefinder which is without efiect since the line circuits terminating bothway junctions are not equipped with meters.

In the event of the called party proving busy the testing wiper -P1 encounters guarding earth instead of battery on the associated contact which prevents the operation of the switching relay 2H, and upon the release of relay E after its slow period, relay M then operates over its upper winding from earth at the resting armature 2712, Fig.

5, armature rcl, off-normal springs 2N2, armatures b2 and Z03, rotary off-normal springs 2NR1, armature 62, upper winding of relay M to battery. Relay M thereupon locks for the remainder of the call by way of its armature ml to earth on the release trunk conductor, at armature m2 connects earth to the common start conductor TPS, to set in operation the tone equipment shown in Figs. 11 and 12, at armature m3 eifects the application of busy tone from the terminal BT corresponding to that shown in Fig. 11, to the upper speaking conductor and the calling subscriber, at armature m4, Fig. 4, interrupted earth is connected to the individual supervisory lamp LP which flashes to indicate the busy holding condition, at armature m5 the impulsing circuit is opened to the rotary magnet 2RM and at armature m6 an alternative holding circuit is completed to relay LO. In this manner the calling subscriber is informed that the desired subscriber is unavailable, and the conditions described are maintained until the circuit is cleared from the distant exchange, whereupon relay L releases and this is followed shortly afterwards by relay B which energizes the release magnet ZM to re- Relay BB, however, remains held for a short period after the release of relay B to guard the circuit by maintaining earth on the release trunk conductor 21 and holds operated relay L0 to disconnect the.

idle marking battery to the register translator group. Upon the release of relay BB earth is removed from the release trunk conductor so that the switching relay 1H in the finder and relay LK in the line circuit are released and the following circuit may now be traced for effecting the energization of the finder release magnet in order that the wipers may be restored to the normal position; earth on the contacts associated with armature 11, Fig. 4, armatures M2 and b172, finder release conductor 20, armature 1h2, Fig. 2, oil-normal springs 1N1, winding of release magnet ZM to battery. All apparatus is now restored to the normal position.

Considering now the case of a local subscriber desiring a local connection it is necessary for this purpose to take into use a register controller. Moreover as the local calling subscriber is likely to be one of three types that is, party line, coinbox or ordinary, it is necessary on at least two of these types of connection to extend a discrimi- Q nating signal to the register controller taken into use, in order to prepare it for the transmission of a translated code corresponding tothe class of subscriber who has originated the call. For this purpose party line subscribers and coinbox subscribers are situated on levels 9 and 0 respectively of the line finder multiple and whenever these levels are selected by a finder the necessary discriminating signal is extended forward to the register controller by way of the vertical bank and wiper. The operation of the switch shown in Figs. 4 and 5 is similar to that already described in connection with anincoming call from a distant exchange, in that when the calling line is extended by way of the finder, relay L, Fig. 4, operates and in turn energizes relays B, BB and C to prepare the circuit forthe reception of the impulses, but since the finder will have switched through on a level other than the first, which it will be remembered was allocated for incoming calls only, a discriminating signal is not sent forward over conductor 28 and therefore relay LO, Fig. 4, remains in its normal position. In consequence therefore, when relay B operates at armature b3, idle marking battery is extended over conductor 32 to mark a characteristic contact in the multiple banks of a group of selector finders such as SFS shown in Figs. 6 and '7, one

' of which is associated with each register convancement of the wipers troller. Upon the operation of relay BB at ar mature bb earth is connected by way of the resting armatures Z01 and 120.1 to the common start start conductor 33 which extends to the register controller distributor circuit shown in Fig. 10. For convenience in the drawings this lead is not shown as continuous but is terminated in either figure on terminal points which bear the same designation.

It will, now be convenient to describe the operation of the register controller distributor circuit, the function of which is to preselect an idle register controller and thereafter to connect with each register controller in turn in order that the load shall be evenly distributed; Although not shown in the drawings an auxiliary distributor circuit is provided, arranged to be brought into service when the regular distributor fails or becomes associated with a faulty register controller.

Considering nowthe circuit details and assuming for thepurposes of the description that at this instant the wipers of the distributor switch RDS, Fig. 10, are stood on contacts associated with a register controller which is already in use, wiper 4e will encounter earth over conductor 34 connected up by the operation of the switching relay KB in the register controller. Fig. 6, or alternatively by the operation of the springs 2BK of the busy key which is provided forthe purpose of artificially busying the register controller in the case of a'fault or during test conditions. A circuit is now complete by way of wiper 4e of the switch RDS, Fig. 10, for op-' erating the interrupter relay 3G, in series with the low resistance left-hand winding of relay K which remains inoperative owing to the high resistance winding of relay 3G. Relay 3G at armature 3g1 energizes the driving magnet RDM of the switch RDS which prepares for the ad.-

contacts and at the conclusion of the magnet stroke the associated springs rdm are operated thereby opening the circuit of relay 3G which releases and in turn de-energizes the driving magnet RDM to enable the wipers to be on to the next set of bank contacts. In this manner an alternate action takes place between relay 3G and the magnet until the wipers of the switch RDS come into engagement with contacts extending to a free register controller as indion to the next set of moved cated by the presence of marking battery encountered over wiper 4e. tinuous rotation of the distributor switch wipers in the event of all register controllers being taken into use, one of the contacts associated with wiper 4e shown in the drawings as contact 22 is wired out to a busy common lead 35 which connects with the back contact in parallel of KA relays in all register'controllers in the group. Consequently when all register controllers are taken into use at the same instant, all KA relays will be operated and earth is removed from the busy common lead 35 to arrest the wipers of the distributor switch RDS in'this position. No further circuit operations take place until a call is originated in the manner described, and by the operation of the start relay ST, at armature To prevent the con" stl earth is connected to the common start con- K is operated on both itswindings in series from earth on the busy common 35 to idle marking battery connected up over wiper 4e, which is of low resistance to short-circuit the interrupter relay 36 against operation at this time. Relay K in operating at armature kl completes a looking circuit for itself over its left-hand winding which is sufiiciently low in resistance to guard the register controller from further selection, at armatures k2, k3 and k4 prepares a circuit for the subsequent interaction of relay 3G with the driving magnet of the selector finder, and at armatures k5 and k6 transfers the alarm circuit to the other alarm relay 1TB since it is now proved that the distributor circuit has completed its switching function satisfactorily and the fault, if any, must now lie in the register controller.

It will be remembered from the foregbing description that the selector requiring connection to a register controller is marked by battery in the multiple of the selector finders such as SFS, and assuming for the purpose of the description that the wipers of the selector finder switch taken into use are resting on contacts other than those marked, wiper 80'! will encounter a disconnection and the following circuit then becomes effective in operating relay 3G of the distributor in series 1 with relay KA of the register controller: earth at armature M, Fig. 10, wipe13e and bank contact, conductor 36, right-hand winding of relay KA, armature kal, interrupter springs sfm associated withthe driving magnet of the switch SFS, conductor 37, bank contact and wiper 2c of the distributor switch EDS, Fig. '7, armature k3, winding of relay 3G to battery. Relay 3G at armature 391 extends earth by way of wiper 1e and conductor 38 to energize the driving magnet SFM of the sender finder switch to prepare for the advancement of the wipers into their next position and at the conclusion of the magnet stroke, the interrupter springs sgfm open the circuit to .relay 3G which releases and in turn de-ener'gizes the driving magnet SFM to enable the mechanical movement of the wipers to take place. In this manner relay 3G is now caused to interact with the driving magnet of the selector finder switch in order that the wipers shall be moved into engagement with the selector requiring connection. When the marked position is reached wiper 8d of the switch SFS encounters idle marking battery over conductor 32 from the selector, which is of low resistance to short-circuit the interrupter relay 3G thereby terminating the hunting operation, and the current in the circuit of relay KIA is now increased sufficiently to enable it to operate'over both its windings in series. Relay KA locks on its left-hand winding which is of low resistance and shuntsthe idle marking battery to such an extent as to prevent another register controller from switching in on to the same selector. Relay KA at armatures k2;- lc3, k4, I05 and k6 extends the register controller byway of the wipers of the switch SF'S to the calling selector and at armature ka'? operates relay KB, Fig. 6, which at armature kbl' connects drrect earth instead of marking battery to the test contact associated with wiper 4c of the distributor switch RDS. This connection short-circuits relay K in the distributor circuit so that it releases to enable relay 1G to interact with the driving magnet RDM to move the wipers into engagement with the next idle register controller. This feature is effective even though the start relay S'I' remains operated from calls originated simultaneously so that under all conditions the distributor switch RDS is caused to search for another register controller.

In case a fault occurs in the distributor circuit which prevents relay K switching to a free register controller relay lTA is operated from the earth pulse extended over conductor FDS from the time pulse equipment so that it locks on its other winding by way of armature ltal and at armature 1ta2 connects relay lTC in circuit'with the other time pulse conductor FDZ. If the fault persists for the full period for which the timing device is set, namely in this instance 9 seconds, an earth pulse is extended over the conductor FDZ to operate relay 1TC which thereupon looks over its right-hand winding to earth on the com-- mon conductor 39 extending to an alarm reset key not shown. The locking circuit of relay lTC it will be noticed-extends by way of a resting armature of relay lTC of the other distributor circuit which is shown as enclosed in a dotted rectangle to indicate its remote association. Relay 1T0 moreover at armature 1tc3 connects earth to a common conductor 40 extending to a main alarm circuit which may be of any well-known type and at armature 1tc5 transfers the incoming start conductor 33 to conductor 41 extending to the start relay ST of the other distributor circuit, sothat all calls originated during this period will be completed over the second distributor circuit.

In case a fault occurs'in the register controller which prevents it from switching. in on the selector requiring connection, relay K of the dis-.- tributor will have operated under these conditions and upon the reception of the earth pulse over the conductor FDS relay 1TB is operated and locked, and at armature1tb2 again prepares the circuit for relaylTC to the pulse conductor FDZ. If the fault persists for the full period, upon the connection of earth to the conductor FDZ relay 1TC is again operated andlocked to fulfil the functions already explained, and in ad'- dition since relay 1TB is operated at this time, earth is extended by way of the water 4e to mark the faulty register controller as busy in order to prevent the second distributor switch from becoming associated therewith.

Returning now to the register controller and assuming that the call in question is. proceeding satisfactorily upon the operation of relay KB at armature kb2, Fig. 7, a circuit is completed to the impulser IP which is provided one'per register controller and comprises a pendulum vibrator mechanism arranged to operate two sets of impulsing springs designated in the drawings OPS and SPS, Fig. '7 Springs OPS are included in the line circuit, for delivering trains of impulses to the automatic switches, while springs SPS are arranged to control the stepping of what is known as the sender switch which serves to count off the required trains of impulses in accordance with markings made on its bank contacts; at armature 7cb2 earth is connected to the common start lead TPS extending to the timing and tone equipment shown in Figs. 11 and 12 and at armature kb5, Fig. 7, earth is connected to the holding conductor 42.

Consequent upon the switching through of the register controller relay A, Fig. 5, of the calling selector is operated over the circuit: earth via the lower winding of relay A, armature 2h6, conductor 43, bank contact and. wiper 2d of the switch SFS, Fig. '7, armatures ka3, b136, lm4 and lca2, wiper 1d and bank contact of the switch SFS, conductor 44, armatures 2h5 and c4, windingof relay A to battery. Relay A in operating its armature al, Fig. 4, completes a circuit for operating relay BA which locks byway of its armature bal at the same time opening the start circuit traced over conductor 33 to the distributor switch, at armaturebaZ, same'figure, transfers the impulsing circuit for the driving magnets of this switch to the control of relay A, and at armature ba3 connects earth to the release trunk conductor 21. The circuit is now in a condition to respond to the dialled impulses and in order that the calling subscriber shall be signalled to this effect, dialling tone is extended-from the register controller over a circuit which may be traced from the feed terminal DT, Fig. 6, extending from Fig. 11 of the tone equipment, condenser 45, armature 1m6, 13115 and ka6, wiper 6d and bank contact of the switch SFS, conductor 46, oiT-normal springs 2N3, Fig. 5, low capacity condenser QD to the upper speaking conductor extending to the calling subscriber's instrument.

Generally the operation of the register controller is already well-known-in essentials and a full description of the operation of a similar register controller is given for instance in U. S. Patent No. 1,901,156, granted March 14, 1933, so that a brief description only is given of the main switching features without reference to detailed circuits. Itwill be sufficient to say that when the calling subscriber operates the dial to deliver the first digit of the six which are necessary with the particular numbering scheme under consideration, relay L in the selector, Fig. 4, responds and repeats these impulses to the vertical magnet BCV of the two-directional BC of the units switch into their second position where they connect up the rotary magnet BCR of the BC switch. The second train of impulses are therefore effective in setting the wipers of "the BC switch into engagement with a particular set of contacts from which a code may be set up in accordance with the cross connecswitch designated BCS in Fig. s.- Relay 1o which 

